The subject of this invention is a machine tool for machining panels and plates which is fitted with a number of workpiece clamping devices able to move along the work bench of the said machine tool.
The use of special machine tools such as cutting machines, flanging machines, vertical milling machines and machining centres in general is already known in the panel and plate machining field.
In machine tools, machining is effected by a combination of the composition of the movements-of the work bench and/or the operating head.
The panels and plates are secured to the work bench by special clamping devices, preferably constituted by sucker blocks, ie. blocks containing one or more openings through which air is sucked to clamp the panels against the support during machining. Each block preferably has at least one ball which can partly emerge from the top surface as a result of the action of elastic equipment and/or pressurised air, and disappear below the level of the top surface as a result of the action of air suction devices.
During positioning of the panel to be machined, the said ball partly emerges from the support surface of the block; the operator can thus position the panel with minimal effort, as the friction produced is only rolling friction.
In some machine tools, the workpiece can also be positioned longitudinally with the aid of motor-driven belts.
These motor-driven belts can then descend vertically to prevent possible collisions with the tool during the operating stage.
The technique of fitting the clamping devices, suction blocks or workpiece holders to devices allowing them to move on the workbench is also known. For example, the blocks in question can be fitted on first guides, parallel to the transverse axis of the machine tool bench, which engage second guides parallel to the longitudinal axis of the bench.
This system enables the blocks to be moved and locked in various positions, depending on the size of the panel and the areas to be machined, prevents these workpiece holders from interfering with the route of the cutting blade, for example in the case of cutting machines, and at the same time enables the workpiece to be exploited to the full by minimising machining waste.
The transverse guides are associated with devices, preferably pneumatic devices, designed to lock the transverse guides onto the longitudinal guides in the desired position.
Similarly, the blocks are associated with devices, preferably pneumatic devices, designed to lock the blocks onto the transverse guides in the desired position.
Currently, the transverse guides and clamping devices or blocks are positioned manually by the machine tool operator before a new production run is commenced.
The block positioning operation involves a considerable loss of time and a degree of skill on the part of the operator.
When frequent changes in production take place, ie. when the machine is used for small production runs or the semi-manufactured goods are of different sizes, the down time or stoppages caused by the necessary repositioning of the clamping devices seriously affects the total working time, and therefore the total production costs.